The objectives of this proposal are the design, synthesis and evaluation of specific inhibitors of human placental armotase (estrogen synthetase). These inhibitors include enzyme-generated irreversible inhibitors as well as competitive reversible inhibitors. Specific inhibitors of human placental aromatase should be valuable tools in studying estrogen biosynthesis in placental tissue and in other tissues. They may also be of value in the study and treatment of estrogen-dependent tumors. They may also be helpful in studying the role played by peripheral aromatization of androgen in male endocrinolog.